Question: Before the previous stop there were 98 people riding on a train. 31 people ended up getting off at the stop. How many people are riding the train now?
Answer: The number riding the train now is the difference between the number who were riding and the number who got off at the previous stop. The difference is $98 - 31$ people on the train. $98 - 31 = 67$ people are on the train.